I have make a beer kit (bitter red) and it seems to loose carbonation when I refigerate it. room temp. its fine, I have used rice sugar and its been setting about 3 weeks now... Other than that it tasts great. (not flat just no head when cold)

Warm beer tends to foam more than cold beer. If your beer is a little undercarbonated it might seem flat when cold. About two weeks at room temperature should be long enough to complete carbonation. Did you add 1/2 to 3/4 cup corn sugar per 5 gallons when you bottled?